1. Field of the Invention
The present invention relates to an apparatus for detecting a driving condition of an automotive vehicle, and more particularly to an apparatus for detecting a driving condition such as street travel, mountain travel, highway travel or the like of an automotive vehicle equipped with an electrically power-assisted steering system.
2. Description of the Prior Art
In a conventional hydraulic power-assisted steering mechanism, a ratio of a total steering torque applied to the steerable road wheels and a manual steering torque applied to the steering shaft is controlled in dependence upon a vehicle speed, a steering angle, a steering speed, a road condition and the like to enhance steering feel and stability. To further enhance the steering feel and stability, it is required to control the foregoing ratio in accordance with a driving condition such as street travel, mountain travel, highway travel or the like of the vehicle. It is also desirable that such a driving condition of the vehicle is adapted as an improtant parameter for automatic control of a suspension system, a height control system, a proportion of braking forces acting on front and rear road wheels or the like. Theoretically, such a driving condition of the vehicle can be detected by detection of distribution of rotation angles of the steering shaft in relation to a travel distance of the vehicle. In this method, it is, however, required to use an expensive steering angle detector. Additionally, it is impossible to detect a driving condition of the vehicle in relation to a manual steering torque applied to the steering shaft.